Color has three main components: Hue, Tone and Saturation.
Hue is described as the shade, tint or sensation of a color. The GIA GemSet® has 31 Hues which can be used to describe viturally all colored gemstones. The complete GIA GemSet® has 324 sample hue colors with varying Tones and Saturations.
Tone is described as the relative lightness or darkness of a Hue. The GIA Tone Scale is divided into 11 grades, 0 to 10, with 0 being colorless to 10 being black.
Saturation is described as the strength or purity of a Hue. The GIA Saturation Scale is from 1 to 6. The lower numbers such as 1, 2 or 3 of warm colors such as red, orange or yellow and tend to look brownish and the cool colors such as blue and green tend to look grayish. Level 4 no longer shows either grayishness or brownishness, while neither is strong or weak. Level 5 is strong and level 6 being vivid, almost over colored.
Hue Tone RP/PR red-purple or purple-red 0 c - Colorless or White stpR strongly purplish red 1 exl - Extremely light slpR slightly purplish red 2 vl - Very light R red 3 l - Light oR orangy red 4 ml - Medium light RO/OR red-orange or orange-red 5 m - Medium rO reddish orange 6 md - Medium dark O orange 7 d - Dark yO yellowish orange 8 vd - Very dark oY orangy yellow 9 exd - Extremely dark Y yellow 10 bl - Black gY greenish yellow YG/GY yellow-green or green-yellow styG strongly yellowish green Saturation yG yellowish green 1 gr(br) - grayish (brownish) slyG slightly yellowish green 2 slgr - slightly grayish(brownish G green 3 vslgr - very slightly grayish(brownish) vslbG very slightly bluish green 4 mst - moderately strong bG bluish green 5 st - strong vstbG very strongly bluish green 6 v - vivid GB/BG green-blue or blue-green vstgB very strongly greenish blue gB greenish blue vslgB very slightly greenish blue B blue vB violetish blue bV bluish violet V violet bP bluish purple P purple rP reddish purple Exceptions: Pk pink Brn brown Exceptions added by The Spectrum Network: W white N none, colorless or clear B black
Code Description D Colorless Rarest White River Finest White (Blue White) E Colorless Rarest White River Finest White (Blue White) F Colorless White Top Wesselton Fine White G Near Colorless White Top Wesselton Fine White H Near Colorless White Wesselton White I Near Colorless Tinted White Top Crystal Commercial White J Near Colorless Tinted White Crystal Top Silver Cape K Faint Yellow Yellowish Top Cape Silver Cape L Faint Yellow Yellowish Top Cape Silver Cape M Faint Yellow Yellowish Cape Light Cape N Very Light Yellow Yellowish Cape Light Cape O Very Light Yellow Yellowish Light Yellow Cape P Very Light Yellow Yellowish Light Yellow Cape Q Very Light Yellow Yellowish Light Yellow Cape R Very Light Yellow Yellow Yellow Dark Cape S Light Yellow Yellow Yellow Dark Cape T Light Yellow Yellow Yellow Dark Cape U Light Yellow Yellow Yellow Dark Cape V Light Yellow Yellow Yellow Dark Cape W Light Yellow Yellow Yellow Dark Cape X Light Yellow Yellow Yellow Dark Cape Z Light Yellow Colors that go beyond Z Light Fancy Yellow Fancy Yellow Intense Yellow
Diamonds also come in a wide spectrum of other colors and are described by their primary color and its degree of intensity.
Color Encyclopedia of Gemstones by Joel E. Arem, PH.D.,F.G.A. , GAA Market Monitor by Donald A. Palmieri, Gemstones of the World by Walter Schumann, Handbook of Gem Identification by Richard T. Liddicoat, Jr., Minerals of the World by Rudolf Duda and Lubos Rejl,